U.S. Pat. No. 6,788,504 to Vanderkolk discloses a mobile system for use in supplying AC power to different types of electrical loads including those having grounded neutrals as well as those having neutrals that are electrically isolated from ground. The system includes a GFCI circuit and can be switched between a first mode, in which the circuit provides AC power with ground fault protection for those loads having ungrounded (isolated) neutrals, and a second mode, in which the GFCI is deactivated so that it will not experience false tripping due to the intentional grounding of the neutral at the load. Both single and multi-phase systems are disclosed which can be incorporated into a vehicle, towed trailer, or portable generator. The system may be used to provide AC power to various types of electrical loads at locations where public utility power is not readily available.
U.S. Pat. No. 6,052,266 to Aromin discloses a ground fault circuit interrupter (GFCI) that interrupts the flow of current through a pair of lines extending between a source of power and a load. The GFCI includes a circuit breaker having a switch located in one of the pair of lines. The switch has a first position in which the source of power in its associated line is not connected to the load and a second position in which the source of power in its associated line is connected to the load. A relay circuit is coupled to the switch selectively positioning the switch in either the first or second position. The relay circuit includes a solenoid, which operates in either an energized or de-energized state. The GFCI also includes a booster circuit for selectively supplying a first voltage through the switch and to the solenoid, which is sufficient to cause the solenoid to switch from its de-energized state to its energized state. A power supply circuit supplies a second voltage to the solenoid, which is less than the first voltage. The second voltage is sufficient to maintain the solenoid in its energized state after being initially energized by the first voltage. A latch circuit operable in first and second bi-stable states allows the solenoid to switch from its de-energized state to its energized state. A fault detecting circuit detects the presence of a fault condition in at least one of the lines and causes the latch circuit to latch in its second bi-stable state upon detection of the fault condition.
U.S. Pat. No. 5,786,971 to Chan et al. discloses a ground fault protection circuit for plural loads connected across a power source with plural branches that can be used where the loads are unbalanced. Each branch includes a ground fault circuit interrupter device that has a common line for the electronics of the GFCI separate from the neutral line from the power source to the load, where the common lines for the electronics for the ground circuit interrupter devices in each branch are connected to a common point. The ground fault protection circuit employs plural ground fault circuit interrupter devices and eliminates nuisance tripping. The common line for the electronics for a GFCI is routed through the core of the current sensing transformer of the GFCI. The separate neutral line for the electronics, connecting the common lines for the electronics for plural GFCI devices and routing the common lines for the GFCI electronics through the core of the transformer of each GFCI, eliminate improper GFCI operation due to unbalanced loading. The ground fault protection circuit may be used for a three phase power source.